A fly-wheel unit for an internal combustion engine comprises a first fly-wheel and a second fly-wheel having a common rotational axis and being angularly movable with respect to each other about said rotational axis. A torque transmission unit is provided for torque transmission between said first fly-wheel and said second fly-wheel. Said torque transmission unit includes a central disc substantially coaxial with said fly-wheels and two cover plates on both axial sides of said central disc. At least one group of substantially axially aligned windows is provided in said central disc and said cover plates, respectively. These windows accommodate a torsion spring.